Starts and runs good on the ground, then quits in flight, returning to the ground and it starts and runs well again. Doesn't that sound more like something loose? A broken wire that loses connectivity when moved? A loose wire at the plug cap? Wire at a switch or battery? Sounds to me like the ignition is probably working just fine by itself, but something is interrupting the flow of electricity to the end point.

If everything in the ignition checks out the you'll need to revisit the fuel system to see if it's venting properly.